Some weird problem for my display. Very dark but still can see.

Hello guys,

I replaced the CD player to dual hard drives last night. I have successfully installed osx high sierra on my new SSD. But when I used for a while, the display suddenly went dark. The weird thing is I still can see the desktop through my cellphone's light and it still work. At the beginning the display can be displayed at some angle. but toady it's all dark(macbook still can work but I need to use cellphone's light to light it). That's so funny...

I have tried to change back to the old HDD, and teardowned all cables, screws, even display and put it back again. But still can't solve the problem. All cables and logic board seems well. Did I broke something when I changed the hard drive?

hope someone could help me. Very thankful.

(btw before I teardowned my MBP yesterday. My display didn't have any problem)